Van Pelt had been in the hospital for some time due to a deteriorating medical condition, Bengs said.

He was convicted for the murder while lying in wait and the torture of Frank Aguilar on Jan. 22, 1985, CDCR officials said.

Van Pelt mistakenly believed Aguilar was responsible for killing his friend Raymond Ziegler, according to the CDCR.

Van Pelt was sentenced to death in Riverside County on July 12, 2002 and was admitted to San Quentin six days later, CDCR officials said.

Since 1978, when California reinstated capital punishment, 54 condemned inmates have died of natural causes, 18 have committed suicide, 13 have been executed in California, one was executed in Missouri and six died from other causes, according to the CDCR.